The present invention relates to a method of driving an AC plasma display panel used as an image display in a television receiver, a computer monitor, or the like.
In a conventional AC plasma display panel (hereinafter referred to as a xe2x80x9cpanelxe2x80x9d), as shown in FIG. 3, plural pairs of a scanning electrode 2 and a sustain electrode 3 are provided on a first glass substrate 1 in parallel with one another, and a dielectric layer 4 and a protective film 5 are provided so as to cover the pairs of the scanning electrode 2 and the sustain electrode 3. On a second glass substrate 6, a plurality of data electrodes 8 covered with a dielectric layer 7 are provided. On the dielectric layer 7, separation walls 9 are provided between every two of the data electrodes 8 in parallel to the data electrodes 8. Phosphors 10 are provided on the surface of the dielectric layer 7 and on side faces of the separation walls 9. The first glass substrate 1 and the second glass substrate 6 are positioned opposing each other with a discharge space 11 being sandwiched therebetween so that the scanning electrode 2 and the sustain electrode 3 are orthogonal to the data electrodes 8. A discharge cell 12 is formed between two adjacent separation walls 9 at the intersection of a data electrode 8 and a pair of the scanning electrode 2 and the sustain electrode 3. In the discharge spaces 11, xenon and at least one selected from helium, neon, and argon are filled as discharge gases.
The electrode array in this panel has a matrix form of Mxc3x97N as shown in FIG. 4. In the column direction, M columns of data electrodes D1 to DM are arranged, and N rows of scanning electrodes SCN1 to SCNN and sustain electrodes SUS1 to SUSN are arranged in the row direction. The discharge cell 12 shown in FIG. 3 corresponds to the region shown in FIG. 4.
FIG. 5 shows a timing chart of an operation driving waveform in a conventional driving method for driving this panel. In FIG. 5, one subfield is shown. One field for displaying one picture includes a plurality of subfields. The conventional driving method of driving this panel is described with reference to FIGS. 3 to 5 as follows.
As shown in FIG. 5, all the data electrodes D1 to DM and all the sustain electrodes SUS1 to SUSN are maintained at an electric potential of 0 (V) in an initialization operation in the first part of an initialization period. To all the scanning electrodes SCN1 to SCNN, a positive-polarity initialization waveform is applied, which increases rapidly from the potential of 0 (V) to an electric potential Vc (V) and then increases more gradually up to a potential Vd (V). At the potential Vc, the voltages of the scanning electrodes SCN1 to SCNNwith respect to all the sustain electrodes SUS1 to SUSN are below the firing voltage, and at the potential Vd, those voltages are beyond the firing voltage. During the gradual increase in the initialization waveform, first weak initialization discharges occur in respective discharge cells 12 from all the scanning electrodes SCN1 to SCNNto all the data electrodes D1 to DM and all the sustain electrodes SUS1 to SUSN, respectively. Thus, a negative wall voltage is stored at the surface of the protective film 5 on the scanning electrodes SCN1 to SCNN. At the same time, positive wall voltages are stored at the surfaces of the phosphors 10 on the data electrodes D1 to DM and at the surface of the protective film 5 on the sustain electrodes SUS1 to SUSN.
In an initialization operation in the second part of the initialization period, a potential Vq (V) is applied to all the sustain electrodes SUS1 to SUSN. At the same time, to all the scanning electrodes SCN1 to SCNN, a waveform is applied, which decreases rapidly from the potential Vd to a potential Ve (V) and then decreases more gradually to a potential Vi (V), thus completing the application of the initialization waveform. At the potential Ve, the voltages of the scanning electrodes SCN1 to SCNNwith respect to all the sustain electrodes SUS1 to SUSN are below the firing voltage, and at the potential Vi, those voltages are beyond the firing voltage. During the gradual decrease in the initialization waveform, second weak initialization discharges occur in the respective discharge cells 12 from all the data electrodes D1 to DM and all the sustain electrodes SUS1 to SUSN to all the scanning electrodes SCN1 to SCNN. Thus, the negative wall voltage at the surface of the protective film 5 on the scanning electrodes SCN1 to SCNNand the positive wall voltages at the surface of the protective film 5 on the sustain electrodes SUS1 to SUSN and at the surfaces of the phosphors 10 on the data electrodes D1 to DM are weakened to wall voltages suitable for a write operation. Thus, the initialization operation in the initialization period is completed.
In a write operation in the subsequent write period, the potential Vq is applied to all the sustain electrodes SUS1 to SUSN continuously. Initially, a potential Vg (V) is applied to all the scanning electrodes SCN1 to SCNN. Then, to the scanning electrode SCN1 in the first row, a scanning waveform of a potential Vi is applied, which has a polarity opposite to that of the initialization waveform and is the same potential as the potential Vi at the end of the initialization waveform. At the same time, a data waveform of a potential Vb (V) with the same polarity as that of the initialization waveform is applied to a designated data electrode Dj (j indicates one or more designated integers of 1 to M) that is selected from the data electrodes D1 to DM and corresponds to a discharge cell 12 to be operated so as to emit light in the first row. In this state, the potential difference between the surface of the protective film 5 on the scanning electrode SCN1 and the surface of the phosphor 10 at the intersection (a first intersection) of the designated data electrode Dj and the scanning electrode SCN1 is calculated by subtracting the negative wall voltage at the surface of the protective film 5 on the. scanning electrode SCN1 from the sum of the potential Vb of the data waveform and the positive wall voltage at the surface of the phosphor 10 on the data electrode Dj (i.e. by adding the absolute values of them). Therefore, at the first intersection, a write discharge occurs between the designated data electrode Dj and the scanning electrode SCN1. At the same time, this write discharge induces a write discharge between the sustain electrode SUS1 and the scanning electrode SCN1 at the first intersection. Thus, at the first intersection, a positive wall voltage is stored at the surface of the protective film 5 on the scanning electrode SCN1, and a negative wall voltage is stored at the surface of the protective film 5 on the sustain electrode SUS1.
Then, to the scanning electrode SCN2 in the second row, a scanning waveform of a potential Vi is applied. At the same time, a data waveform of a potential Vb is applied to a designated data electrode Dj that is selected from the data electrodes D1 to DM and corresponds to a discharge cell 12 to be operated so as to emit light in the second row. In this state, the potential difference between the surface of the protective film 5 on the scanning electrode SCN2 and the surface of the phosphor 10 at the intersection (a second intersection) of the designated data electrode Dj and the scanning electrode SCN2 is calculated by subtracting the negative wall voltage at the surface of the protective film 5 on the scanning electrode SCN2 from the sum of the potential Vb of the data waveform and the positive wall voltage at the surface of the phosphor 10 on the data electrode Dj. Therefore, at the second intersection, a write discharge occurs between the designated data electrode Dj and the scanning electrode SCN2. At the same time, this write discharge induces a write discharge between the sustain electrode SUS2 and the scanning electrode SCN2 at the second intersection. Thus, at the second intersection, a positive wall voltage is stored at the surface of the protective film 5 on the scanning electrode SCN2, and a negative wall voltage is stored at the surface of the protective film 5 on the sustain electrode SUS2.
Successively, the same operation is carried out for all remaining rows up to the N row, thus completing the write operation in the write period.
In a sustain operation in a sustain period subsequent to the write period, a sustain waveform of a potential Vh (V) is applied alternately to all the scanning electrodes SCN1 to SCNNand all the sustain electrodes SUS1 to SUSN. Thus, in the discharge cells 12 in which the write discharges have occurred, sustain discharges are caused successively. Visible emission from the phosphors 10 excited by ultraviolet rays generated by the sustain discharges is used for display.
In an erase operation in an erase period subsequent to the sustain period, to all the sustain electrodes SUS1 to SUSN, an erase waveform is applied, which increases gradually from a potential of 0 (V) to a potential Vr (V). Thus, in the discharge cells 12 in which the sustain discharges have occurred, during the gradual increase in the erase waveform, a weak erase discharge occurs between a sustain electrode SUSi (i indicates one or more designated integers of 1 to N) and a scanning electrode SCNi. Therefore, the negative wall voltage at the surface of the protective film 5 on the scanning electrode SCNi and the positive wall voltage at the surface of the protective film 5 on the sustain electrode SUSi are weakened, thus terminating the discharges. Thus, the erase operation in the erase period is completed.
However, in such a conventional driving method, a potential amplitude Vb of the data waveform is 80V, which is high. Therefore, a circuit for driving the data electrodes (a data-electrode driving circuit) used in this method is required to have a high withstand voltage of at least 80V, which causes a problem of high cost. Further, the power consumption of the data-electrode driving circuit is determined depending on: (data-electrode capacitance)xc3x97(repeated frequency of the data waveform)xc3x97(potential amplitude of the data waveform)2xc3x97(the number of data electrodes). Therefore, for instance, in the case of a 42-inch-wide VGA panel, the maximum electric power consumption of the data-electrode driving circuit is 200 W, which is extremely high. This also has been a problem.
The present invention is intended to solve such problems and to provide a method of driving a panel, which enables cost reduction by lowering the withstand voltage of a data-electrode driving circuit and reduction in power consumption of the data-electrode driving circuit.
A method of driving an AC plasma display panel of the present invention is used for driving an Ac plasma display panel including: a first substrate and a second substrate, which are arranged opposing each other with a discharge space being sandwiched therebetween; plural pairs of a scanning electrode and a sustain electrode that are covered with a dielectric layer and are arranged on the first substrate; and a plurality of data electrodes orthogonal to and opposing the scanning electrode and the sustain electrode, which are provided on the second substrate. The driving method of the present invention employs an initialization period for applying, to the scanning electrode, an initialization waveform of a ramp voltage and a write period for applying, to the scanning electrode, a scanning waveform having a polarity opposite to that of the initialization waveform sequentially, and at the same time, applying, to the selected data electrodes, a data waveform having the same polarity as that of the initialization waveform. The potential of the scanning electrode during the application of the scanning waveform is set to be lower than that of the scanning electrode at the end of the application of the initialization waveform. In addition, the potential of the sustain electrode during the application of the scanning waveform is set to be lower than that of the sustain electrode at the end of the application of the initialization waveform.
According to this method, the potential amplitude of the data waveform applied to the data electrodes can be reduced. Therefore, the withstand voltage of a data-electrode driving circuit can be lowered and the cost of the data-electrode driving circuit can be reduced. Moreover, the power consumption of the data-electrode driving circuit also can be reduced.